The present invention relates to a joint apparatus for an automobile exhaust pipe.
In an automobile engine, in a case where exhaust gases from exhaust ports of respective cylinders are introduced into a muffler through a manifold, if an attempt is made to introduce the exhaust gases, which have passed through the manifold, into the muffler by means of an integrating exhaust pipe immediately after the manifold, the exhaust gases interfere with each other, deteriorating the exhaust efficiency. When the exhaust of an ensuing cylinder is started when the exhaust gases in the exhaust pipe are in the state of low pressure, the exhaust gases of the cylinder are forcibly exhausted, and the exhaust efficiency improves. Therefore, a means has been proposed in which, in a four-cylinder system, for example, the exhaust gases from cylinders whose timings of intake, compression, combustion, and exhaust are utterly reverse are made to converge, respectively, so as to enhance the exhaust efficiency.
In such a case, to prevent the transmission of vibrations from the manifold side to the muffler side, a joint apparatus in which each of a pair of juxtaposed exhaust pipes and each of a pair of mutually coupled branch pipes of a bifurcated exhaust pipe are coupled to each other is used immediately after the manifold. As shown in FIG. 2, this joint apparatus is generally provided with a pair of spherical joints 74 and 75 having common flanges 71 and 72 and resilient means 73. The spherical joint 74 is provided with a spherical annular seal member 78 fitted over an outer surface of an exhaust pipe 77 coupled to an exhaust port of a first cylinder by means of a manifold 76, while the spherical joint 75 is provided with a spherical annular seal member 80 fitted over an outer surface of an exhaust pipe 79 coupled to a fourth cylinder by means of the manifold 76. The common flange 71 is secured to the exhaust pipes 77 and 79, while the common flange 72 having spherical seats 83 and 84, on which spherical annular surfaces 81 and 82 of the spherical annular seal members 78 and 80 are respectively seated slidably, is secured to each of branch pipes 86 and 87 of a bifurcated exhaust pipe 85 coupled to the muffler side. The resilient means 73 is constituted by two resilient devices 61 and 62 which are symmetrically fitted to the flanges 71 and 72. Each of the resilient devices 61 and 62 is provided with a bolt 90 disposed in such a manner as to be passed through the flanges 71 and 72, a nut 88 meshing with the bolt 90, and a coil spring 89 interposed between a head of the bolt 90 and the flange 72. The resilient means 73 causes the two flanges 71 and 72 to approach each other by the resilient forces of the coil springs 89 so as to cause the spherical seats 83 and 84 to be resiliently pressed against the spherical annular surfaces 81 and 82.
In the joint apparatus shown in FIG. 2, the relative swinging motion of the bifurcated exhaust pipe 85 and the exhaust pipes 77 and 79 is allowed by the sliding motion of the spherical seats 83 and 84 with respect to the spherical annular surfaces 81 and 82. However, in the relative swinging motion in a direction perpendicular to the plane of the drawing of FIG. 2, the spherical seats 83 and 84 are slid with respect to the spherical annular surfaces 81 and 82 without causing a gap between each of the spherical annular surfaces 81 and 82 and each of the spherical seats 83 and 84, whereas in the relative swinging motion in a direction parallel to the plane of the drawing, gaps can be caused alternately between the spherical annular surface 81 and the spherical seat 83 and between the spherical annular surface 82 and the spherical seat 84, thereby possibly causing the exhaust gases from leaking through the gaps.